LLMCLI_MUTE_THINKING=1 suppresses reasoning text

Fallback to Converse API for models without streaming support

Allow “thinking” and prompt caching on Claude 4 models

Cache system prompt if possible

Improve terminal detection and escape sequence handling

Replace custom terminal detection with golang.org/x/term library.

Lift formatting out of Chunks method

Chunks method now returns richer type that allows to distinguish between
“thinking” and regular response text. Output stream formatting now
happens within the Chunks method caller code.

While here, also make sure that ansi escape codes are only printed to
stdout, they are not written to the buffer used to accumulate markdown
to be later rendered into html.

Improve Claude 3.7 thinking budget validation

Consolidate logic within the flag parsing function.

Format Claude 3.7 “thinking” output differently

Support “extended thinking” mode of Claude 3.7 Sonnet

Use full filename (as provided) when sending text attachments